In the equation of privacy versus freedom of expression, I worry that in the UK the balance weighs too heavily in favor of privacy. The UK is known for its favorable privacy laws in the Anglo-Saxon world, one of a few reasons why England is home to a disproportionate number of obscenely rich, famous and not-so-famous individuals from all over the world.
This particular case is tittle tattle and doesn't much concern anyone beyond the parties to the case (despite any high falutin, trail blazing claims by MM). There are many, much more significant instances where proper investigative reporting of issues of greater public interest than celebrity gossip might be affected by a precedent of this sort. Instances involving politics, business, the military and national security figures, and the Church. Or, the Royal Family and its dealings.
It's a balancing act. In this case, there was a narrow question for the Court of Appeal to address, and imo they reached the correct answer. The DM was interested only in the revelations about MM that the appeal process allowed them, and that they got. (You lie with dogs, you get fleas.) MM asserted that although the letter could have been leaked and so was drafted by her accordingly, it wasn't drafted in order to be leaked (and no evidence was produced to the contrary). This was key. The printing of the letter was an invasion of her privacy. If the DM wanted to disprove whatever it was (I've never read the letter or the assertions it was printed to deny, I don't know what the actual gossip was), they didn't need to print everything they did. A paragraph or so could have sufficed. In this case, the DM crossed the line (knowingly, imo.They have a war chest for such cases and MM was their target from the moment she started playing them at their game). But the bottom line is that MM knew it was a dirty game, and she went into battle forearmed. In my book, they're as bad as each other and neither is the winner or the loser here. As ever, the lawyers won.
But there will be instances where the individual facing the press won't come to battle tooled up, or will come to battle with more tools than any media group could be expected to commit resources to. There is such little negative reporting of the RF and of the individuals in it that one can't help but wonder. MM may think she's won with this judgement - she has. But if her ultimate aim is to show the RF for what it is, warts and all, I wonder if she hasn't just scored an own goal by handing Charles, William, Andrew or whoever else's turn is next, a privacy precedent on a plate.